title: Single-site bismuth alkoxide catalysts for the ring-opening polymerization of lactide.
abstract: Salen bismuth alkoxides, where the salen ligand contains 2,4-di-tert-butylphenoxy groups and one of ethylene, cyclohexane or ortho-phenyl as a backbone have been prepared from reactions involving Bi[N(SiMe₃)₂]₃ and the free salen ligand followed by alcoholysis (ButOH, PriOH and 2,6-But₂C₆H₃OH). The molecular structures of the salen ligand with the cyclohexyl back-bone have been determined for the complexes salenBiCl and salenBiOC₆H₃-2,6-But₂. The chloro compound is a dimer with chloride bridges while the phenoxide is monomeric with an unusually distorted five-coordinate geometry. The phenoxide and tert-butoxide complexes have been employed in the ring-opening polymerization of lactides (L- and rac-) to give polylactides, PLAs. With rac-LA heterotactic PLA is formed preferentially, Pr = ~0.9, in dichloromethane or toluene at room temperature. The reaction is first order in [Bi] and is notably faster than most aluminum and zinc initiators as well as tin(II) octanoate. These results are discussed in terms of a recent report on the polymerization of LA by Peptobismol® and bismuth subsalicylate.
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University, 100W. 18th Avenue, Columbus, OH 43210-1185, USA.
authors.forename: Vagulejan
authors.initials: V
authors.lastname: Balasanthiran
authors.forename: Malcolm H
authors.initials: MH
authors.lastname: Chisholm
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Durr
authors.forename: Judith C
authors.initials: JC
authors.lastname: Gallucci
mesh_terms: D001729:Bismuth / Q000737:chemistry*; D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry; D018360:Crystallography, X-Ray; D004146:Dioxanes / Q000737:chemistry*; D005029:Ethylenediamines / Q000737:chemistry; D007700:Kinetics; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011091:Polyesters / Q000138:chemical synthesis / Q000737:chemistry*; D012459:Salicylates / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D004146:Dioxanes; D005029:Ethylenediamines; D009942:Organometallic Compounds; D011091:Polyesters; D012459:Salicylates; C033616:poly(lactide); C015715:bismuth subsalicylate; C011452:disalicylaldehyde ethylenediamine; C091880:dilactide; D001729:Bismuth